1. Field of the Invention
The present invention relates to an organic electroluminescence device.
2. Discussion of the Related Art
Generally, an organic electroluminescence device includes an organic layer formed between an electron injecting electrode (cathode) and a hole injecting electrode (anode). In this state, according as an electric charge is injected to the organic layer, an electron and a hole make one pair, and then are extinct, thereby generating light.
The organic electroluminescence device may be formed on a flexible substrate of a transparent material, such as plastic. In addition, the organic electroluminescence device can be operated at a lower voltage below 10V, as compared with a plasma display panel or an inorganic electroluminescence EL display. Also, the organic electroluminescence device realizes low power consumption and great color quality. Furthermore, the organic electroluminescence device can display three colors of red, green and blue, so that the organic electroluminescence divice has attracted great attentions as a next generation display device.
A method for manufacturing the organic electroluminescence device will be description as follows.
(1) First, an anode material is coated on a transparent substrate. For example, the anode material such as ITO (Indium Tin Oxide) is used generally.
(2) Then, a hole injecting layer HIL is formed on the anode material. At this time, the hole injecting layer HIL is generally formed in a method of coating Copper phthalocyanine (CUPC) at a thickness of 10 nm to 30 nm.
(3) After that, a hole transport layer HTL is coated on the hole injecting layer HIL. At this time, the hole transport layer HTL is formed in a method of depositing 4,4′-bis[N-(1-naphthyl)-N-phentylamino]-biphenyl(NPB) at a thickness of 30 nm to 60 nm.
(4) An organic emitting layer is formed on the hole transport layer. In this case, a dopant may be added to the organic emitting layer as needed. In case of the green luminescesnce, tris(8-hydroxy-quinolate)aluminum(Alq3) is deposited at a thickness of 30 nm to 60 nm as the organic emitting layer, and MQD(N-methylquinacridone) is commonly used as the dopant.
(5) Then, an electron injecting/transport layer EITL may be formed on the organic emitting layer, or an electron transport layer ETL and an electron injecting layer EIL may be sequentially formed on the organic emitting layer. In case of the green luminescence, Alq3 has a great electron transport capability, so that there is no requirement for forming the electron injecting/transport layer.
(6) Next, a cathode is formed on the electron transport layer (or electron injecting/transport layer), and then a protecting layer is coated as needed, thereby completing the organic electroluminescence device.
In the aforementioned structure of the organic electroluminescence device, the hole injecting and transport layer has an effect on luminance and driving voltage of the device. That is, the hole injecting and transport layer plays an important part in the life span of the device. Accordingly, it is necessary to research and develop a material for the hole injecting and transport layer, to realize improvement of luminance and decrease on driving voltage.